A wide variety of flat stamped contact devices are now being used in connecting devices for electronic equipment. Flat stamped contact devices have oppositely facing first and second major surfaces and edge surface portions which extend between the major surfaces. The contact areas are on the edge surfaces rather on the flat major surfaces, and the devices are quite thin, for example, 0.014 inches (0.356 mm) or less. The connectors in which flat stamped contact devices are used usually have the contact devices on closely spaced centers, 0.025 inches (0.635 mm) or less. The contact areas on flat stamped contact devices are very narrow and it is important that good electrical contact be established by means of these very narrow contact areas when the devices are put to use.
The nature of the stamping operation is such that the edge surfaces of a stamped part are rough rather than smooth, and do not extend normally of the flat major surfaces. When an opening is produced in strip material, the punch which produces the opening presses a portion of the material into the opening in the die block. Initially, the material is pushed by the force of the punch into the die opening and a relatively smooth burnished surface is produced adjacent to the surface of the strip stock. As the material under the punch is deformed, it work hardens and eventually it fractures producing a rough fractured edge surface. Contact devices are produced by punching a series of openings in strip stock and the contact edge surfaces therefore exhibit this phenomenon of a burnished zone which is relatively flat that extends from one surface of the strip stock partially towards the other. This burnished and flat zone merges with the fractured zone which extends to the other surface of the strip stock. The edge produced does not extend normally of the flat rolled surfaces of the stock but tends to be inclined from the one surface towards the other.
In order to minimize the effects of a conventional punching operation, the tooling can be carefully designed, the material can be selected carefully to produce a minimum fractured zone, and in some cases, the edge can be shaved to provide a smooth surface on the contact edge of the contact device. Shaving does no eliminate all of the problems however for the reason that shaving usually produces a burr extending from one of the surfaces of the contact device and this burr is troublesome when the contact devices are positioned on closely spaced centers.
The present invention is directed to the achievement of flat stamped contact devices having improved contact edge surfaces, and to methods and apparatus for producing improved contact devices.